Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$135.71	9.593%	$148.7287	$148.73	$148.75	$148.70
Purchase #2	$99.66	3.265%	$102.9139	$102.91	$102.90	$102.90
Purchase #3	$44.41	12.725%	$50.0612	$50.06	$50.05	$50.10
Purchase #4	$18.37	6.472%	$19.5589	$19.56	$19.55	$19.60
Purchase #5	$78.92	12.858%	$89.0675	$89.07	$89.05	$89.10
Purchase #6	$160.62	11.631%	$179.3017	$179.30	$179.30	$179.30
Purchase #7	$234.93	12.602%	$264.5359	$264.54	$264.55	$264.50
7 purchase totals =	$772.62		$854.1678	$854.17	$854.15	$854.20